Milk Fatty Acids and Infant Cognitive Development (Part I)
Last week USA TODAY highlighted two papers from Pediatrics indicating that “higher levels of long-chain polyunsaturated fatty acids (LCPUFA) were linked to greater mental development in both young and older children.” But is that what the studies showed? Yes and no- it turns out that the devil is in the details.
Some background: DHA, for example, is an omega-3 fatty acid that is a critical structural component of the brain. DHA, and other LCPUFA naturally occur in mother’s milk and are ingested by the infant during critical periods of neurodevelopment. The prediction is therefore that more fatty acids equals better neurodevelopment equals better cognition. Studies making links in this chain have influenced companies to include fatty acids in infant formulas starting about a decade ago.
The first paper, by Isaacs et al. 2011, reports an experimental study in which pre-term infants were randomly assigned to either a standard formula diet or a fatty acid enhanced formula diet. Interestingly there were NO DIFFERENCES between the two formula groups when cognition was assessed 10 years later- e.g. the fatty acid enhanced formula was not associated with better cognitive performance. This study was initiated before long-chain polyunsaturated fatty acids were typically included in commercially available formulas. But wait, there’s more! Baby girls fed the fatty-acid enhanced formula DID have improved cognitive performance compared to baby girls fed “regular” formula, it was only for boys that there was no effect (stay tuned for future posts about milk and sex-biases!).
The second paper getting people talking was by Guxen et al. 2011 and using a large sample size (>500 subjects!) was able to investigate aspects of breast-feeding (cumulative time spent nursing, duration of exclusive breast-feeding in months), fatty acid composition at the onset of lactation (colostrum only) and infant cognitive performance at 14 months of infant age. The fatty acid composition in milk by itself was not correlated with infant cognitive performance. LCPUFA were only associated with infant cognition as a function of cumulative time spent nursing- mothers who spent more time nursing cumulatively over the first year of the infant’s life AND produced higher concentrations of LCPUFA in colostrum had infants that performed better on cognitive assessments than infants whose moms breast-fed less and had lower LCPUFA.
But it turns out that Guxen and colleagues found that both cumulative time spent nursing AND exclusively breast-feeding for the first 6 months produced infants that performed better on cognitive tests even after controlling for numerous socio-economic, lifestyle, and parental factors. Keep in mind that this study is not experimental and mothers selected to breast-feed and for how often and for how long, so other explanations having to do with mother-infant interactions can not be ruled out. This study is particularly exciting, though, because it looks at variation occurring among breastfeeding mothers and provides evidence that both breastfeeding and specific constituents in milk predict infant cognitive performance later during development.
Further Reading:
Mònica Guxens, Michelle A. Mendez, Carolina Moltó-Puigmartí, Jordi Julvez, Raquel García-Esteban, Joan Forns, Muriel Ferrer, Martine Vrijheid, M. Carmen López-Sabater, and Jordi Sunyer. 2011. Breastfeeding, Long-Chain Polyunsaturated Fatty Acids in Colostrum, and Infant Mental Development. Pediatrics 128:4 e880-e889; published ahead of print
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